Submission #1159508

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Source Code Expand

#include<bits/stdc++.h>
using namespace std;
#define rep(i,a,b) for(int i=a;i<b;i++)


int N, K; string S;
//-----------------------------------------------------------------
inline char getrev(char c, int m) {
	int cc = c - 'A';
	if (m % 2 == 1) cc = 1 - cc;
	return char('A' + cc);
}
//-----------------------------------------------------------------
int main() {
	cin >> N >> K >> S;

	deque<char> deq;
	string ans = "";
	rep(i, 0, N) deq.push_back(S[i]);
	int cnt = 0, rev = 0, done = 0;
	while (!deq.empty()) {
		// 右側を詰める
		while (!deq.empty()) {
			if (getrev(deq.back(), rev) == getrev('A', done)) {
				deq.pop_back();
				ans = getrev('A', done) + ans;
				done++;
			} else {
				break;
			}
		}
		if (deq.empty()) break;

		// 変換
		if (getrev(deq.front(), rev) == 'A') {
			// パターン1
			cnt++;
			char c = deq.front(); deq.pop_front();
			deq.push_front(getrev(c, 1));
		} else {
			// パターン2
			cnt++;
			deq.pop_front();
			rev++;
			ans = getrev('A', done) + ans;
			done++;
		}

		if (cnt == K) break;
	}

	if (!deq.empty()) {
		while (!deq.empty()) {
			ans = getrev(deq.back(), rev) + ans;
			deq.pop_back();
		}
		cout << ans << endl;
		return 0;
	}

	int d = K - cnt;
	if (N % 2 && d % 2) ans[0] = 'B';
	cout << ans << endl;
}

Submission Info

Judge Result